A conventional sampled-data feedback control system, as shown in FIG. 9, may employ sampled sensor data to control an actuator to produce a desired system response. The control system typically implements an application dependent control algorithm, which involves performing calculations on the sample data to produce an output command before the next data sample period.
In various conventional motor control applications, digital signal processors (DSPs) and/or microcontrollers are used to implement control functions, such as digital motor control functions. These implemented control functions may include, for example, field oriented control of induction machines and permanent magnet synchronous machines, AC inverter drives, and high performance servo drives. The software to control these conventional implementations is generally interrupt driven, not completely deterministic in terms of expected input/output, and fixed in computational structure.
The above-described control functions (e.g., motor control functions) may be implemented in one microcontroller, with high speed computational tasks being performed by an Application Specific Integrated Circuit (ASIC). The high speed computational tasks performed by the ASIC may include, for example, pulse width modulated (PWM) waveform generation, encoder signal interface, coordinated transformation, proportional-plus-integral (PID) control, etc.
ASICs are advantageous for use in control applications, since their availability and design flexibility make possible the high computational speeds required for the tasks of various control functions, such as motor control functions. However, since the computational speed of ASICs is limited, ASIC design solutions may not be optimal for today's control applications, which require ever increasing performance and flexibility.
In situations in which a DSP and/or ASIC does not have the necessary computational speed to perform a required task, it is known to divide computational tasks among various DSPs and/or microcontrollers. For example, one DSP or microcontroller may perform torque control, whereas another DSP or microcontroller may perform other functions, such as controlling various parameters in the digital control application. However, by separating functionality among various DSPs and/or microcontrollers, control circuit designs (e.g., motor control circuit designs) may require complex interconnectivity and signaling between various components, thereby increasing design time and dollar cost.
To avoid complex interconnectivity and signaling between various components, it is known to provide additional and/or supplemental functionality in software. However, it is believed that the time and cost of developing application-specific software results in a developmental process that is slower and less cost-efficient. Furthermore, as the complexity of required software increases, the man-hour resources required to program such software increase exponentially, especially for designs requiring that the programming effort be divided among various individuals. Often, specific skills and techniques are required to ensure that the software performs with the computational speed required. Such skills and techniques, while streamlining speed of software code execution, often require additional cost for code maintainability, and often must be implemented in native assembly language to achieve the required computational speed. As a result, a high level language such as C is typically avoided, thereby contributing to a lack of code maintainability.